After Cooler
Functions of compressed air after coolers : –
- Cool air discharged from air compressors via the heat exchanger
- Reduce risk of fire (Hot compressed air pipes can be a source of ignition)
- Reduce compressed air moisture level
- Increase system capacity
- Protect downstream equipment from excessive heat
Coolers are usually sized with a CTD (Cold Temperature Difference) of 5°F, 10°F, 15°F or 20°F (2.7°C, 5.5°C, 8.3°C, or 11°C). This means that the compressed air temperature at the outlet of the aftercooler will be equal to the cooling medium temperature plus the CTD when sized at the specified inlet air temperature and flow.
Recommended location of after coolers : –
The aftercooler should be located as close as possible to the discharge of the compressor.
Types of after coolers : –
There are two basic types of air after coolers:
- air-cooled
- water-cooled.
The type of aftercooler you choose depends on your preference and requirements.
Compressor manufacturers may include aftercoolers within the compressor package. In general these compressors are referred to as integral aftercoolers. A stand-alone or freestanding aftercooler is a separate unit installed downstream of the compressor.
After cooler : –
Air cooled aftercoolers (fig. AC1-2) use ambient air to cool the hot compressed air. The compressed air enters the air cooled aftercooler. The compressed air travels through either finned tubes or corrugated aluminum sheets of the aftercooler while ambient air is forced over the cooler by a motor-driven fan. The cooler, ambient air removes heat from the compressed air.
Belt Guard Air Cooled After cooler : –
A belt guard air-cooled aftercooler mounts to the compressor’s v-belt guard. The compressor’s belt pulley has fins designed to force ambient air over the compressor and air cooled aftercooler. The air passing over the aftercooler facilitates the heat transfer. The pulley also sends air over the compressor helping maintain proper operating temperature.
After cooling sizing considerations : –
Most air aftercoolers are sized to cool the air to within 5 to 20°F (2.7°C to 11°C) of ambient air or cooling water temperature. This is called the approach temperature. Always size for the hottest day with 100% relative humidity. Sizing is dependent on the temperature of the air coming from the compressor. Typically air exiting a compressor is between 180°F (82.2°C) to 350°F (176.6°C).